Neil Marshall's “The Descent” is for my money one of the five greatest horror films of the last decade, a razor-sharp thrill-ride with pitch-perfect claustrophobic dread seeping into full-blooded exhilarating carnage, rounded out with complex moral ambiguity. It is also a perfect stand-alone film which really didn't need a sequel – though after its considerable worldwide success, that's exactly what it has now got.

Picking up 2 days after the events of the first film, the film starts with a search party trawling through the caves trying to locate the missing girls. However they're searching in the wrong place since Juno took them to an uncharted system instead of the planned caves in the first film. So when Sarah (Shauna MacDonald) is found in the woods bruised, bloody and with no memory of the previous 48 hours, the sheriff (Gavin O'Herlihy) quickly arranges a small team to search the caves leading off the old mines nearby. With time running low, the sheriff insists on taking Sarah with the group in the hope she'll recover enough of her memory to provide some guidance and narrow down their search. But none of the group are prepared for the horrors lurking in the caves below.

Following-up “The Descent” was never going to be an easy task, and on paper the alarm bells start ringing. Amnesia is a classic unnecessary sequel cliché for a start, and the cast list insists on bringing back the character of Juno (Natalie Mendoza), who turns out to be not as dead as she clearly was in the first film, but merely limping. Most worryingly, Neil Marshall declined to return to the director's chair, making way for the first film's editor Jon Harris to make his directorial debut.

Against all the odds however, “The Descent: Part 2” manages to recapture the lightening in a bottle of the first film. As editor of the first film, Harris clearly had an intimate knowledge of what made the film tick, and he recreates the magic in a surprisingly confident move-up to director. The title of “Part 2” is oddly somewhat mannered, but actually hugely appropriate – the sequel doesn't feel like a tacked on cash-in new film, but actually a direct continuation of the first, tonally and stylistically. You could watch the two films back-to-back and it would just feel like one long film with little drop-off in quality, surely the biggest compliment I can give. As soon as we get back into the caves that claustrophobic dread returns, and there's a sense that an idiot could have pulled this off. Of course, it's easy to mess up stuff like this (see “The Cave” for proof), but “The Descent: Part 2” pulls it off with such confidence it feels easy. I'm not ashamed to admit that for huge lengths of the film my palms were running with sweat and I could feel my heart thumping fast in my chest – a reaction too few films get from me. Once again, it feels like you're trapped alone in the dark with fearsome monsters all around.

Before we get carried away, lets get those negatives out of the way. Probably the biggest problem with the film is that it is essentially “more of the same”, in a “does what it says on the tin” kinda way. It inevitably lacks the surprise factor of the first film, and doesn't really add anything to the mythology. The complex moral ambiguity of the first film (is Sarah heroine, or anti-heroine?) are bypassed in favour of a clearer redemptive arc for the character which, whilst about the only path to take with the character, is not quite as fascinating and daring. Having said that, the character work, though having a few nice beats, really does take a back-seat to the inevitable bloody carnage. And whilst undeniably effective (the guy sitting next to me literally leapt out of his seat on at least 3 occasions) some of the shocks are well-telegraphed in a clichéd manner – such as having the suspenseful music give way to quiet in order to make the sudden loud shock more effective. There are also a couple of homages (a line of dialogue from “The Thing” here, a 'wall moving behind you' moment from “Aliens” there) which pulled me out of the film a touch – as did an unexpected moment of toilet humour.

As with the first film, a big part of the success of the picture is the gorgeous photography by Sam McCurdy. Again, great swathes of the screen are bathed in darkness, with small pockets of light dancing about, constantly threatening to reveal all manner of evils lurking in the dark, and the audiences' eyes dart around the screen trying to second guess where the next shock will come from. Half-lit rock formations in the background take on menacing visages (kudos too to the production design and art direction team), whilst touches such as the night-vision mode camcorder from the first film reappear, they are not overused and remain effective.

Another key element in the success of the film is the music and sound design. David Julyan returns as composer, reusing the thematic ideas from part 1, and this really is instrumental (sorry) in retaining the atmosphere of the first film – as soon as his music starts up, you're immediately back in the world of “The Descent”. There were some early test screening reviews of the film on-line which were pretty so-so, complaining that the film felt cheap and didn't recapture the atmosphere of the first film. Well, I'm willing to bet that the big difference between that version of the film and this fully-complete version is the sound design. The film is hugely reliant upon its sound design for its creepily atmospheric mood, and from the “Predator”-esque snarl of the crawlers to the horrible metallic shuddering of the mineshaft life, the terrific sound is fully enveloping and effective.

Enough of all that, what's the action like? Pretty damn sweet is the answer. Harris wastes as little time as possible in the set-up to get us back into those caves, and since we already know what's down there in the dark, there's less suspenseful build-up, and it's not that long before the first attack, meaning there's about twice as much crawler action than in the first film – including (unless my eyes were playing tricks in the dark) a female crawler. The film is every bit as bloodily violent as the first one, and although the most bloody gore is crawler rather than human it's still furiously cathartic and provoked several moments of spontaneous applause from the audience at the screening I attended. Without giving too much away, look forward to a revisit to that huge ravine from the first film, a gooey headcrush, a nastily protracted arm-chop, and a horribly nervous trip through flooded caves.

Although it's not really a performance-driven film, the film boasts some strong turns, with the returning MacDonald and Mendoza revisiting their characters with aplomb. Of the newbies, Krysten Cummings as the young policewoman eager to get back to her daughter gets the best role, and thrillingly gives it all she's got, easily able to stand toe-to-toe with the other girls. This is actually her first film role, and it's a highly promising debut. Gavan O'Herlihy also does some great work as the Sheriff, and if the three caving experts (Joshua Dallas, Anna Skellern and Douglas Hodge) don't stand out in the mind quite as strongly, they don't have quite such strong material to work with and are never less than effective.

Overall, for a film that doesn't really need to exist, “The Descent: Part 2” is way better than it reasonably has any right to be. There are moments of blistering, brutal brilliance here to match the first film, although it's not hard to shake the feeling that a third trip into these caves would see overfamiliarity and the law of diminishing returns really starting to take its toll. Right now, the name “The Descent”stands for a high level of quality horror, and with “Part 2” not pulling the name into disrepute, I'd like to see it stay that way. But then a bafflingly bold last-minute twist simply demands to be explored in a third part.